The GMT function is one of the most useful complications a watch can have. What this feature does is allow you to view a second timezone at a glance. It does this by using a fourth hand, in addition to the standard hour, minute & second hands, to display the hour in a different timezone. Whether you have family that lives across the country or you travel for business, this can be a very useful tool.

Rolex first introduced the GMT Master in a collaboration with PanAm Airways in 1954. It was the first wristwatch to display two timezones.

The example displayed here is the newest version from Rolex, the GMT Master II. This version has a two-tone ceramic bezel so you can easily distinguish if it is day or night in your referenced timezone.